U.S. patent number 4,686,332 [Application Number 06/878,949] was granted by the patent office on 1987-08-11 for combined finger touch and stylus detection system for use on the viewing surface of a visual display device.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Robert L. Donaldson, Evon C. Greanias, C. Richard Guarnieri, John J. Seeland, Jr., Guy F. Verrier.
United States Patent |
4,686,332 |
Greanias , et al. |
August 11, 1987 |
Combined finger touch and stylus detection system for use on the
viewing surface of a visual display device
Abstract
A combined finger touch and stylus detection system is disclosed
for use on the viewing surface of the visual display device.
Transparent conductors arranged in horizontal and vertical grid are
supported on a flexible, transparent overlay membrane which is
adaptable to a variety of displays. A unique interconnection
pattern is provided between the transparent conductors in the array
and buses which interconnect the conductors with the supporting
electronics, whereby a minimum number of bus wires can be employed
to service the array conductors and yet both unique finger touch
location sensing and unique stylus location sensing can be
accomplished. The system includes a control processor which
operates on stored program instructions which, in a first
embodiment provides for the alternate detection of either finger
touch location or stylus location and, in a second embodiment,
provides for the simultaneous detection of both finger touch
location and stylus location. The resulting system provides the
unique function of combined finger touch and stylus detection, is
adaptable to a variety of display surfaces, is provided with a
structure which is easily manufacturable, and which has an inherent
long-term reliability.
Inventors: |
Greanias; Evon C. (Chevy Chase,
MD), Guarnieri; C. Richard (Somers, NY), Seeland, Jr.;
John J. (Oakland Park, FL), Verrier; Guy F. (Reston,
VA), Donaldson; Robert L. (Annapolis, MD) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
26664421 |
Appl.
No.: |
06/878,949 |
Filed: |
June 26, 1986 |
Current U.S.
Class: |
345/173;
345/180 |
Current CPC
Class: |
G06F
3/0446 (20190501); G06F 3/04166 (20190501); G06F
3/0445 (20190501); G06F 3/0441 (20190501); G06F
2203/04104 (20130101) |
Current International
Class: |
G06F
3/033 (20060101); G08C 021/00 () |
Field of
Search: |
;178/18,19,20
;340/706,709 ;324/207 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schreyer; Stafford D.
Attorney, Agent or Firm: Hoel; John E.
Claims
What is claimed is:
1. A combined finger touch and stylus detection system for use on
the viewing surface of a visual device, comprising:
an array of horizontal and vertical conductors arranged on the
viewing surface of the visual display device, having an I/O
terminal coupled thereto, for conducting electrical signals between
said terminal and the vicinity of said viewing surface;
a radiative pickup stylus, having an output terminal, for receiving
electromagnetic signals radiated from said array;
a selection means having a switchable path connected to said I/O
terminal of said array and having a control input, for connecting
selected patterns of a plurality of said horizontal and vertical
conductors to said switchable path in response to control signals
applied to said control input;
a capacitance measuring means having an input coupled to said
switchable path of said selection means, for measuring the
capacitance of selected ones of said conductors in said array, in
response to said control signals applied to said control
inputs;
a radiative signal source having an output coupled to said
switchable path of said selection means, for driving selected ones
of said conductors in said array, in response to said control
signals applied to said control input;
a radiative signal measuring means coupled to said radiative pickup
stylus, for measuring said electromagnetic signals received by said
stylus;
a control processor connected to said control input of said
selection means, for executing a sequence of stored program
instructions to sequentially output said control signals to said
selection means;
said control processor connected to said capacitance measuring
means, for receiving measured capacitance values of said conductors
when said selection means, in response to said control signals, has
connected a first pattern of a plurality of said conductors in said
array to said capacitance measuring means, to detect the location
of a finger touch with respect to said viewing surface of said
display device;
said control processor connected to said radiative signal measuring
means, for receiving measured radiative signal values when said
selection means, in response to said control signals, has connected
a second pattern of a plurality of said conductors in said array to
said radiative signal source, to detect the location of said stylus
with respect to said viewing surface of said display device;
whereby, both finger touch location and stylus location with
respect to said viewing surface of said display, can be
detected.
2. The apparatus of claim 1, which further comprises:
an overlay membrane upon which is mounted said array of horizontal
and vertical conductors;
a horizontal bus mounted on said overlay for interconnecting said
vertical conductors to said I/O terminal of said array;
said horizontal bus having a plurality of N bus wires and said
vertical conductors being a plurality of no more than N(N-1)/2
vertical conductors;
said plurality of vertical conductors being arranged with each
adjacent conductor pair thereof being connected to a unique
combination of two of said plurality of horizontal bus wires, the
distance separating adjacent ones of said vertical conductors being
approximately the width of a human finger tip;
said control processor receiving from said capacitance measuring
means, said measured capacitance values of two adjacent ones of
said vertical conductors which are juxtaposed with said human
finger tip, thereby detecting the horizontal location of said
finger tip with respect to said viewing surface of said
display.
3. The apparatus of claim 2, which further comprises:
said plurality of vertical conductors being further arranged with
each conductor of any group of a subplurality of adjacent
conductors thereof being connected to a unique one of said N
horizontal bus wires;
said control processor controlling said selection means to connect
selected ones of said vertical conductors in said group to said
radiative signal source;
said radiative pickup stylus, when proximate to said group,
receiving electromagnetic signals radiated from said selected ones
of said vertical conductors in said group, said received signals
being distinguishable by said radiative signal measuring means over
signals radiating from more distant ones of said vertical
conductors located outside of said group in said array, thereby
detecting the horizontal location of said stylus with respect to
said viewing surface of said display.
4. The apparatus of claim 3, which further comprises:
a vertical bus mounted on said overlay for interconnecting said
horizontal conductors to said I/O terminal of said array;
said vertical bus having a plurality of N bus wires and said
horizontal conductors being a plurality of no more than N(N-1)/2
horizontal conductors;
said plurality of horizontal conductors being arranged with each
adjacent conductor pair thereof being connected to a unique
combination of two of said plurality of vertical bus wires, the
distance separating adjacent ones of said horizontal conductors
being approximately the width of a human finger tip;
said control processor receiving from said capacitance measuring
means, said measured capacitance values of two adjacent ones of
said horizontal conductors which are juxtaposed with said human
finger tip, thereby detecting the vertical location of said finger
tip with respect to said viewing surface of said display.
5. The apparatus of claim 4, which further comprises:
said plurality of horizontal conductors being further arranged with
each conductor of any group of a subplurality of adjacent
conductors thereof being connected to a unique one of said N
vertical bus wires;
said control processor controlling said selection means to connect
selected ones of said horizontal conductors in said group to said
radiative signal source;
said radiative pickup stylus, when proximate to said group,
receiving electromagnetic signals radiated from said selected ones
of said horizontal conductors in said group, said received signals
being distinguishable by said radiated signal measuring means over
signals radiating from more distant ones of said horizontal
conductors located outside of said group in said array, thereby
detecting the vertical location of said stylus with respect to said
viewing surface of said display.
6. The apparatus of claim 5, wherein N=16 and said subplurality is
8.
7. The apparatus of claim 5, which comprises:
said overlay membrane including an inner laminate and an outer
laminate;
said inner laminate including an inner substrate consisting of a
sheet of polyethylene terephthalate upon which is deposited said
plurality of vertical conductors;
said plurality of vertical conductors being composed of a group
consisting of indium tin oxide, gold and silver;
said inner laminate further including an insulation layer composed
of vinyl acrylic polymer deposited over the surface of said
vertical conductors, with a plurality of apertures therein
selectively positioned over each of said vertical conductors;
said horizontal bus having said N bus wires composed of silver
deposited on the surface of said insulation layer and penetrating
through selected ones of said apertures in said insulation layer to
make electrical contact with selected ones of said vertical
conductors;
said outer laminate including an outer substrate consisting of a
sheet of polyethylene terephthalate upon which is deposited said
horizontal conductors and over which is deposited a second
insulation layer including apertures therein exposing selected ones
of said horizontal conductors, and further including said vertical
bus having said N bus wires thereof formed by silver deposited on
said second insulation layer and penetrating selected ones of said
apertures therein to make electrical contact with selected ones of
said horizontal conductors;
said inner laminate and said outer laminate being joined by an
adhesive material, forming a unitary flexible transparent
membrane.
8. The apparatus of claim 5, which further comprises:
said overlay membrane including an inner laminate and an outer
laminate;
said inner laminate including an inner substrate consisting of a
sheet of polyethylene terephthalate upon which is deposited said
plurality of horizontal conductors;
said plurality of horizontal conductors being composed of a group
consisting of indium tin oxide, gold and silver;
said inner laminate further including an insulation layer composed
of vinyl acrylic polymer deposited over the surface of said
horizontal conductors, with a plurality of apertures therein
selectively positioned over each of said horizontal conductors;
said vertical bus having said N bus wires composed of silver
deposited on the surface of said insulation layer and penetrating
through selected ones of said apertures in said insulation layer to
make electrical contact with selected ones of said horizontal
conductors;
said outer laminate including an outer substrate consisting of a
sheet of polyethylene terephthalate upon which is deposited said
vertical conductors and over which is deposited a second insulation
layer including apertures therein exposing selected ones of said
vertical conductors, and further including said horizontal bus
having said N bus wires thereof formed by silver deposited on said
second insulation layer and penetrating selected ones of said
apertures therein to make electrical contact with selected ones of
said vertical conductors;
said inner laminate and said outer laminate being joined by an
adhesive material, forming a unitary flexible transparent
membrane.
9. A method for detecting either finger touch or stylus location in
an overlay membrane having horizontal conductors and vertical
conductors selectively connected to a capacitance measuring device,
a radiative source, and further including a stylus pickup connected
to a radiative signal measurement device for measuring the strength
of electromagnetic signals radiated from the conductors on the
overlay as picked up by the stylus, the steps comprising:
determining whether a finger touch threshold has been exceeded;
locating the finger touch if said touch threshold is exceeded;
determining whether a stylus threshold is exceeded, if said touch
threshold was determined not to have been exceeded;
locating the position of the stylus if said stylus threshold has
been exceeded;
repeating said step of determining whether said touch threshold has
been exceeded, if said stylus threshold has not been exceeded;
whereby both finger touch and stylus detection can be alternately
carried out for said overlay membrane.
10. A method for simultaneously detecting both finger touch
location and stylus location on an overlay membrane including an
array of horizontal conductors and vertical conductors which are
selectively connected to a capacitance measuring means, a signal
source, and which includes a stylus connected to a radiative pickup
measurement means for measuring the electromagnetic radiation
emitted by said conductors in said overlay and picked up by said
stylus; the steps comprising:
cyclically detecting the remote proximity of the stylus from the
overlay and detecting the finger touch on said overlay in a
proximity loop;
passing control to a stylus location step to identify the
coordinates for the location of said stylus with respect to said
overlay, followed by sensing any possible finger touch to said
overlay;
starting a tracking loop to cyclically update the coordinates for
the location of said stylus with respect to said overlay and
detecting any possible finger touch to said overlay;
repeating said tracking and said finger touch sensing steps in said
tracking loop until the detected magnitude of said signals picked
up by said stylus become less than a threshold value;
passing control to said proximity loop;
whereby coordinates for both stylus location and finger touch
location on said overlay can be output during said locate cycle and
said tracking loop.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The invention disclosed broadly relates to data processing
technology and more particularly relates to input devices for use
in conjunction with visual displays.
2. Background Art
In data processing systems, a central processor executes a sequence
of stored program instructions to process data provided by an input
device and to present the results of the data processing operations
to an output device. Data processing results can be presented in
either alphanumeric text or in graphical form and a universal
mechanism for manifesting those results is by means of a visual
display device such as a cathode ray tube monitor, a gas panel
display, an array of light emitting diodes, or other types of
visual display devices. Frequently, the results presented to the
user on a visual display device, will require the user to provide
additional data to the data processing system. Various types of
data input devices have been employed in data processing systems,
for example keyboard input, graphical tablet input, and various
forms of display surface inputs. Human factors studies have shown
that by providing a means for inputting data on the visual display
screen itself, the user can achieve the most closely coupled
interactive operations with the data processing system. When the
user responds to visual signals output at the face of the visual
display device, by inputting signals at that same visual display
surface, an accuracy and immediacy in the interaction between man
and machine can be achieved. This form of input device is easy to
learn to use and seems the most natural and user-friendly to the
operator
Various types of interactive input devices for use at the display
surface have been provided in the prior art. One of the first forms
of interactive devices was the light pen, which is an optical
detector provided in a hand-held pen, which is placed against the
display surface of a cathode ray tube screen. When the dot of light
represented by the scanning raster is detected by the light pen,
the coordinates of the raster dot are attributed as the location of
the hand-held pen. Another type of interactive input device for use
on a display surface is the mechanical deformation membrane, which
is a transparent laminate placed over the display surface. The
laminate consists of two conductor planes respectively deposited on
a flexible medium so that when the user mechanically displaces one
of the conductor planes by a finger touch, the conductors are
brought into electrical contact with the conductors in the second
plane. The electrical resistance of the conductor plane is changed
as a function of the position of the finger touch on the membrane
and appropriate electronics are provided to translate that
resistance value into the position attributed to the finger
touch.
Opaque graphics tablets, upon which a sheet of drawing paper can be
supported for tracing with an electronic stylus, have been provided
in the prior art. In opaque graphics tablets, a horizontal wire
grid and a vertical wire grid are embedded in the surface of the
tablet. The wires in the tablet are driven with a signal which is
electromagnetically radiated from the surface of the tablet and
which is received by a pickup stylus connected to a signal
detector. In one type of opaque graphics tablet, a field gradient
is imposed from one side to the other side of the tablet and the
strength of the field as picked up by the stylus, is correlated
with the position attributed to the stylus. Another approach has
been described by H. Dym, et al. in U.S. Pat. Nos. 3,992,579;
3,999,012; and 4,009,338, those patents being assigned to the IBM
Corporation. Dym, et al. describe driving the conductors embedded
in the opaque graphics tablets so that they are selectively
energized with 40 kilohertz signals in a multiple stage operation
to first determine the stylus proximity to the surface of the
tablet and then to track the position of the stylus along the
surface of the tablet in the horizontal and vertical directions.
During the proximity stage of operation, the conductors in all
regions of the tablet surface emit signals which are detected by
the stylus as it approaches the surface. When the amplitude of the
received signals is great enough, the operation then changes into
the locate and tracking mode which is programmed to produce
periodic indications of the stylus position with respect to the
horizontal and vertical conductors embedded in the tablet.
The popularity of the Personal Computer can be attributed, in part,
to the enhanced productivity which can be achieved by applying data
processing techniques to the execution of tasks which were
previously done manually. Typical applications employing an
interactive input at the display surface of the monitor in a
Personal Computer, require the operator to make control selections
at the keyboard, perhaps selecting the mode of operation or
particular image to be displayed, prior to using the interactive
input device for inputting data to the system. For example, in
hotel management applications, the operator would enter control
information at the keyboard to select either a first displayed
image for a room assignment application or a second displayed image
for entering billing information. Only after having made the
control input at the keyboard, will the operator be able to make
data entries by means of the interactive input at the display
surface.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide an improved
interactive input device for a display surface.
It is another object of the invention to provide an interactive
input device which permits either finger touch input or stylus
detection input modes.
It is yet a further object of the invention to provide an improved
interactive input for a display surface which can be adapted to a
variety of surface contours.
It is yet a further object of the invention to provide an improved
interactive input for a display surface which is reliable and is
inexpensive to manufacture.
It is yet a further object of the invention to provide an
interactive input device for use at a display surface, which
permits the simultaneous detection of both a finger touch and a
stylus position.
DISCLOSURE OF THE INVENTION
A combined finger touch and stylus detection system is disclosed
for use on the viewing surface of a visual display device. The
system includes an array of horizontal and vertical conductors
arranged on the viewing surface of the visual display device,
having an I/O terminal coupled thereto, for conducting electrical
signals between the terminal and the vicinity of the viewing
surface. A radiative pickup stylus is also included, having an
output terminal, for receiving electromagnetic signals radiated
from the array.
The system includes a selection means having a switchable path
connected to the I/O terminal of the array and having a control
input, for connecting selected patterns of a plurality of the
horizontal and vertical conductors to the switchable path in
response to control signals applied to the control input. A
capacitance measuring means is also included, having an input
coupled to the switchable path of the selection means, for
measuring the capacitance of selected ones of the conductors in the
array, in response to the control signals applied to the control
input.
The system further includes a radiative signal source having an
output coupled to the switchable path of the selection means, for
driving selected ones of the conductors in the array, in response
to the control signals applied to the control input. A radiative
signal measuring means is also included, coupled to the radiative
pickup stylus, for measuring the electromagnetic signals received
by the stylus.
In addition, the system includes a control processor connected to
the control input of the selection means, for executing a sequence
of stored program instructions to sequentially output the control
signals to the selection means. The control processor is connected
to the capacitance measuring means, for receiving measured
capacitance values of the conductors when the selection means, in
response to the control signals, has connected a first pattern of a
plurality of the conductors in the array to the capacitance
measuring means, to detect the location of a finger touch with
respect to the viewing surface of the display device. The control
processor is also connected to the radiative signal measuring
means, for receiving measured radiative signal values when the
selection means, in response to the control signals, has connected
a second pattern of a plurality of the conductors in the array to
the radiative signal source, to detect the location of the stylus
with respect to the viewing surface of the display device.
In this manner, both finger touch location and stylus location with
respect to the viewing surface of the display, can be detected.
The system can be used for both sequential and simultaneous
detection of finger touch and stylus position. The system makes use
of a unique interconnection arrangement for the horizontal and
vertical conductors to respective buses which are of a reduced
size, thereby saving space and driver electronics. A unique overlay
membrane structure supports the horizontal and vertical conductors
of the array and has sufficient mechanical flexibility to enable it
to conform to the surface contour of a variety of display
surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other advantages of the invention will be more
fully, understood with reference to the description of the best
mode and the drawing wherein:
FIG. 1 is a front view of the overlay 20 and the mounting frame
22.
FIG. 2 is a side cross-sectional, breakaway view of the overlay and
mounting frame of FIG. 1, along with section line 2--2'.
FIG. 3 is a side view of the overlay 20 and the stylus 60 for
stylus detection.
FIG. 4 is a schematic view of the overlay for stylus detection.
FIG. 5 illustrates the radiative signal amplitude for measuring
pair P0 in stylus detection.
FIG. 6 shows the measurement for the pair P1 for stylus
detection.
FIG. 7 shows the measurement for the pair P2 for stylus
detection.
FIG. 8 is a cross-sectional view of the overlay 20 and the finger
70 for finger touch detection.
FIG. 9 is an architectural diagram of the detection system.
FIG. 10 is a flow diagram of the operation of the first embodiment
of the invention for detecting either finger touch or stylus
position.
FIG. 11 is a rear view of the general layout of the overlay 20.
FIG. 12 is a side cross-sectional view of the overlay 20 along the
section line 12--12' of FIG. 11, showing the detail of the display
input area.
FIG. 13 is a front breakaway view of the overlay 20 in the bus
region.
FIG. 14 is a side cross-sectional view along the section line
14--14' of FIG. 13.
FIGS. 15A; 15B; 15C are a front view of the layout of the X bus for
the overlay 20.
FIGS. 16A, B, & C are a flow diagram of a second embodiment of
the invention, when both finger touch and stylus detection can be
simultaneously carried out.
FIG. 17 is a timing diagram for the second embodiment of the
invention, for the simultaneous detection of both finger touch and
stylus location.
FIG. 18 is a diagram of the memory organization for the RAM 102 in
the second embodiment of the invention.
FIG. 19 is a front view of the display as seen through the overlay
20, showing the simultaneous finger touch and stylus detection, in
accordance with the second embodiment of the invention.
DESCRIPTION OF THE BEST MODE FOR CARRYING OUT THE INVENTION
The combined finger touch and stylus detection system is shown in a
front view in FIG. 1 and in a side cross-sectional view in FIG. 2,
in association with a cathode ray tube display. The overlay 20
consists of two sheets of durable, transparent plastic, with an
array of horizontal transparent conductors embedded in the first
sheet and an array of vertical transparent conductors embedded in
the second sheet. The overlay 20 can be mounted by means of the
frame 22 onto the display surface 32 of the cathode ray tube 24.
The mounting frame 22 consists of a base portion 28 which attaches
to the sidewall 26 of the cathode ray tube (CRT) 24. The front
facing surface 30 of the base portion 28 can have a curvature
substantially the same as the curvature of the display surface 32.
The overlay 20 is mechanically flexible and can be laid directly
upon the surface 32 of the CRT so that its edges overlap the
surface 30 of the base portion 28 for the mounting frame 22. The
clamping member 34 can then be placed over the edges of the overlay
20 so that the mating surface 38, which has a curvature similar to
that of the surface 30, clamps the edges of the overlay 20. The
mounting bolts 36 secure the member 34 to the base portion 28.
FIG. 2 shows a cross-sectional view of the overlay 20 positioned on
the display surface 32 of the CRT. The overlay is stretched
slightly by the mounting frame, to provide a smooth, tight and well
supported surface for finger touch and stylus detection. The
overlay shown in FIG. 3 consists of the inner substrate 50 which is
a sheet of polyethylene terephthalate which is transparent,
electrically insulative, and has a thickness of approximately 0.002
inches. An array of horizontal transparent conductors is deposited
on the surface of the inner substrate 50 and are designated as Y1,
Y2, Y3, etc., with the Y3 wire being shown in FIG. 3. The
transparent conductors can be composed of indium tin oxide, for
example, which is a well-known transparent conductor material. The
thickness of the transparent conductor can be approximately 1000
angstroms. The conductors are approximately 0.025 inches wide and
are spaced approximately 0.125 inches on a center-to-center
spacing. An insulation layer 52 covers the horizontal Y wires and
can be composed of a transparent adhesive such as ultraviolet
initiated vinyl acrylic polymer having a thickness of approximately
0.002 inches. The upper portion of the overlay 20 shown in FIG. 3
consists of the outer substrate 54 which is a sheet of polyethylene
terephthalate which is optically transparent, electrically
insulative and has a thickness of approximately 0.002 inches.
Deposited on the surface of the outer substrate 54 is a vertical
array of transparent conductors designated X1, X2, X3 . . . X6 . .
. . The conductors X1, etc. are also composed of indium tin oxide
and have a thickness of approximately 1000 angstroms, a width of
approximately 0.025 inches and a spacing of approximately 0.125
inches, center-to-center. The outer substrate 54 and the vertical
conductors X are joined by the adhesive insulation layer 52 to the
inner substrate 50 and the horizontal wires Y. The X and the Y
transparent conductors can also be composed of gold and silver or
other suitable materials. The thickness of the conductors is
adjusted to provide resistance below 50 ohms per square and an
optical transmission which is greater than 80 percent.
FIG. 3 depicts the arrangement for detection of the stylus 60 when
it is closer than the locate threshold distance 62. The principle
of operation in the stylus detection mode is that the X and/or Y
conductors are driven by a 40 kilohertz oscillator driver so that
the X and/or Y conductors act as a transmitter of electromagnetic
radiation and the stylus 60 acts as a receiver of that radiation.
To transmit a signal, the oscillator selectively drives either the
X conductors or the Y conductors. The stylus 60 detects the signal
and electronics connected to the stylus digitizes the magnitude of
the signal. The magnitude of the signal detected by the stylus is a
function of the height of the stylus above the overlay 20. By
comparing this magnitude to known thresholds, the height of the
stylus above the overlay can be determined. When the stylus signal
has reached the contact threshold corresponding to the locate
threshold distance 62, the operation of stylus detection can shift
from proximity detection to a location and tracking mode. The
object of tracking the stylus is to have the X conductors and the Y
conductors in the overlay driven in such a manner that the
radiation picked up by the stylus 60 can enable the attribution of
an instantaneous position for the stylus.
The basic drive pattern for determining the stylus position is
schematically shown in FIG. 4. A wire pair is defined as two
adjacent X conductors, for example, with the left-hand conductor
and several conductors to the left thereof being either grounded or
connected to a first reference potential and the right-hand
conductor and several conductors to the right thereof being driven
by the oscillator driver. FIG. 4 shows the wire pair P0 located
beneath the stylus 60, with the conductor X3 being the left-handed
conductor and the conductor X4 being the right-handed conductor.
The conductors X1, X2 and X3 are connected to ground potential
whereas the conductors X4, X5 and X6 are connected to the
oscillator driver. FIG. 5 shows the amplitude of the signal
received by the stylus 60 as it would pass from left to right from
above the conductor X1 to a position above the conductor X6. Note
that within and around the wire pair X3 and X4, the stylus signal
varies linearly with position. This linearity is the basis for an
accurate interpolation technique for providing a precise measure of
the position of the stylus 60 based upon the measurement of
radiation from three wire pairs. The first stage in the measurement
is measuring the amplitude for the wire pair P0. FIG. 6 shows the
second stage in the measurement where the wire pair P1 is formed
with the conductors X4 and X5. The plot of the magnitude of the
signal received by the stylus 60 which remains fixed at its
location shown in FIGS. 4 and 5, would indicate a lower relative
measured amplitude for the wire pair P1 measurement. The final data
in the three stage operation of locating the position of the stylus
60 is shown in FIG. 7, where the wire pair P2 is the inverse of the
wire pair P0. That is, the conductors X1, X2 and X3 are driven with
the oscillator driver, whereas the conductors X4, X5 and X6 are
connected to ground or reference potential. The signal amplitude is
shown for the wire pair P2 in FIG. 7. Once again, with the stylus
60 remaining in the same position that it had for FIGS. 4, 5 and 6,
the magnitude of this signal for the wire pair P2 will be
measured.
The calculation of the horizontal position of the stylus 60 with
respect to the vertical X conductors X1, X2, X3, etc. is done in
two stages. First, the base coordinate is calculated and then
second an offset coordinate is calculated which is added to the
base coordinate to form the resultant measured position. To
calculate the base coordinate, the system calculates the number of
wires between the origin of coordinates at the left-hand edge of
the overlay and the first wire adjacent to the axis of the stylus
60. This number of wires is multiplied times the pitch of the X
conductor separation, in this case 0.125 inches, to obtain the base
coordinate value. The base coordinate produced is the midpoint
between the wire pair X3 and X4 in this example.
The offset coordinate is the coordinate of the stylus relative to
the midpoint of the wire pair X3 and X4. The offset coordinate is
equal to the wire separation pitch in the horizontal direction
times (P0-P2) divided by 2x(P0-P1). The numerator of this
expression is a linear expression within a wire pair whereas the
denominator is a constant. Both of these terms depend upon the
angle of the stylus with respect to the tablet which can vary
during normal operation. The division operation cancels this
dependence, allowing the expression to be invariant as to the angle
at which the stylus is held. The resulting ratio varies linearly
between approximately -1 and +1 and, when multiplied times the
pitch, gives an additive factor which, when added to the base
coordinate, results in the interpolated value for the horizontal
position of the stylus with respect to the vertical X conductors.
The resolution for this measurement is typically 0.01 inches. A
similar operation is conducted for the horizontal conductors Y1,
Y2, etc. to establish the vertical position of the stylus with
respect to the horizontal conductors.
It is seen that in order to locate position of the stylus with
respect to the vertical conductors, the vertical conductors must be
arranged with each conductor in any group of at least six adjacent
conductors, uniquely connected to the oscillator driver. A similar
condition must also prevail for the horizontal Y conductors. As was
previously mentioned, in order to obtain an approximately 0.01 inch
resolution, a grid pitch of approximately 0.125 inches must be
maintained for the conductors in both the horizontal direction and
in the vertical direction. If a display area of 12-13 inches in the
horizontal and the vertical direction is to be covered by the
overlay, then approximately 100 vertical X conductors and 100
horizontal Y conductors will be required in the overlay 20. If 200
different drivers were required to drive all 200 conductors, the
mechanical and electrical complexity necessary to make that
connection would be prohibitive. It is clearly advantageous to
provide some means for reducing the number of driver wires which
interconnect the conductor wires in the array to the oscillator
driver. Dym, et al. have provided in their above cited patents, a
busing technique which employs a horizontal bus having 24 separate
driver wires each of which are respectively connected to several
vertical conductors in the opaque graphics tablet disclosed
therein. The horizontal conductors are similarly arranged and are
connected through a vertical bus also having 24 wires. Taking the
vertical array conductors for example, the 24 wires in the
horizontal bus feeding the vertical array conductors were
classified into three sets of eight wires each. The vertical array
conductors were divided into groups. To make the individual groups
of array conductors unique for the purposes of detection by the
stylus, the order of the array conductors is changed for every
group. This reduced the number of drive wires in the bus since each
wire in the bus was connected to and drove multiple array
conductors. The separation between array conductors connected to
the same bus wire has to be large enough so that signals sensed in
one region of the array are not influenced by the other conductors
in the array connected to the same bus wire.
The problem with the arrangement of the array conductors as
described by Dym, et al. for their opaque graphics tablet, is that
it cannot be used for the capacitive detection of a finger touch
such as is illustrated in FIG. 8. The finger 70, when touching the
surface of the outer substrate 54 in FIG. 8, will, at best,
approximately cover only two adjacent array conductors, in the case
illustrated, X3 and X4. If the location of the finger 70 is to be
measured with the resolution equivalent to the pitch of the
conductors, in this case 0.125 inches, then the capacitance change
for a first conductor and for an adjacent second conductor must be
measured. In the case of FIG. 8, the capacitance CF3 between the
finger 70 and the X3 conductor must be measured and the capacitance
CF4 between the finger 70 and the conductor X4 must be measured.
The capacitance of all the X conductors X1-X5 and all of the Y
conductors can be measured, but the finger location is determined
by identifying the two adjacent vertical X conductors and the two
adjacent horizontal Y conductors having the maximum change in their
capacitance. The array conductors must be connected to their bus
drive wires in such a manner that each adjacent pair of array
conductors constitutes a unique combination which is never
duplicated elsewhere on the array. One of the problems solved by
the invention disclosed herein is how to combine both finger touch
detection and stylus location detection using the same array of
horizontal and vertical conductors connected through their
respective drive buses.
FIG. 11 is a rear view over the overlay 20 showing the general
layout of the overlay. The X bus 80 consists of 16 drive wires 1,
2, . . . 16 and similarly the Y bus 90 consists of 16 bus wires.
The X bus 80 is connected through the X connector 182 to the drive
electronics. Similarly, the Y bus connector 184 connects the Y bus
90 to the drive electronics. The display input area 188 has the
transparent array conductors arranged therein with the vertical
transparent conductors X1-X112 selectively connected to the bus
wires 1-16 in the X bus 80. Correspondingly, the horizontal
transparent conductors Y1-Y112 are selectively connected to the 16
bus wires of the Y bus 90. FIG. 13 is a front detailed view of the
X bus 80, showing the bus wires 1, 2, 3, 4 and 5 of the X bus 80.
Two vertical transparent array wires X1 and X2 are shown
respectively connected to the X bus wires 1 and 3, for example.
FIG. 14 is a cross-sectional view of FIG. 13, showing how the
horizontal bus wire 3 connects through an aperture 180 in the
insulation layer 52 to make connection to the transparent wire X2.
The actual pattern for interconnecting the 16 bus wires 1-16 the X
bus 80 to the 112 vertical, transparent array conductors X1-X112,
is shown for the X bus layout in FIG. 15. The order of connection
is also given in Table I.
In the preferred embodiment, the number of vertical array
conductors X1, X2, . . . , which must be capable of independent
control, is a function of the pitch of the wires in the array (the
number per unit distance in the horizontal direction), the number
of position determinations per unit time (the sampling rate of the
wires in the array), and the maximum speed of the stylus movement
which is desired to be accommodated. Using the wire pair concept
shown in FIGS. 4-7, let the number of wires to the left of the wire
pair (including the left-hand member of the pair) be the quantity M
and let there also the same number M of wires to the right of the
wire pair (including the right-hand member of the pair). The total
quantity of 2M adjacent wires represents a group, which must span a
horizontal distance great enough to exceed the maximum allowable
distance which will be displaced by the stylus during one interval
between successive position determinations (the sampling interval).
In each group of adjacent 2M wires, each wire must be uniquely
connected to one of the plurality of bus wires in the horizontal
bus 80. The same is equally true for the horizontal array
conductors Y1, Y2, . . . .
For example, if the maximum speed of the stylus is 48 inches per
second, the sampling rate is 100 position determinations per
second, the pitch of the wires is 0.125 inches, then the quantity
of M will be four wires on each side of the wire pair. In this
example, the array must be organized so that each group of eight
adjacent wires has each wire therein uniquely connected to the bus
wires in its corresponding bus, in order to accurately track the
position of the stylus moving at up to 48 inches per second. A
wiring pattern which will accommodate this example is shown in
Table I and in FIG. 15.
TABLE I
__________________________________________________________________________
Sequence With Four-Wires-On Tracking Drive No. 16 1 14 2 13 3 12 4
11 5 10 6 9 7 8 15 Occurrence 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 N to
Self -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- N to Four --
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Drive No. 2 1 3 14 4
13 5 12 6 11 7 10 8 9 15 3 Occurrence 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
3 N to Self 12 15 12 16 12 16 12 16 12 16 12 16 13 16 14 12 N to
Four 10 9 10 9 10 9 10 9 10 10 11 11 9 10 10 10 Drive No. 16 2 4 1
5 14 6 13 7 12 8 11 9 16 10 15 Occurrence 2 3 3 3 3 3 3 3 3 3 3 3 3
3 3 3 N to Self 31 16 13 17 13 17 13 17 13 17 13 17 16 12 18 16 N
to Four 11 10 11 10 11 10 11 10 11 12 9 10 11 10 11 9 Drive No. 4 3
5 2 6 1 7 14 8 13 9 12 10 11 15 5 Occurrence 4 4 4 4 4 4 4 4 4 4 4
4 4 4 4 5 N to Self 13 17 12 17 13 17 13 17 13 17 13 17 13 17 14 12
N to Four 10 10 11 10 11 10 11 10 11 10 11 11 9 10 11 10 Drive No.
16 4 6 3 7 2 8 1 9 14 10 13 11 16 12 15 Occurrence 4 5 5 5 5 5 5 5
5 5 5 5 5 5 5 5 N to Self 31 14 13 17 13 17 13 17 13 17 13 17 14 12
18 16 N to Four 11 10 11 10 11 10 11 10 11 11 9 10 11 10 11 10
Drive No. 6 5 7 4 8 3 9 2 10 1 11 14 12 13 15 7 Occurrence 6 6 6 6
6 6 6 6 6 6 6 6 6 6 6 7 N to Self 13 17 13 17 13 17 13 17 13 17 13
17 13 17 13 12 N to Four 11 10 11 10 11 10
11 10 11 10 11 10 9 10 11 10 Drive No. 16 6 8 5 9 4 10 3 11 2 12 1
13 16 14 15 Occurrence 6 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 N to Self 31
16 13 17 13 17 13 17 13 17 13 17 14 12 18 16 N to Four 11 10 11 10
11 10 11 10 11 11 9 10 11 12 15 16
__________________________________________________________________________
To reduce the number of elements in the X bus 80, each bus wire
1-16 drives multiple X array conductors X1-X112. The separation
between those X array conductors which are attached to the same bus
wire, must be large enough so that signals sensed in one region of
the overlay 20 are not affected by the other conductors connected
to that same bus wire. The bus attachment pattern must isolate
conductors attached to the same bus wire, by a sufficient distance
to avoid confusion errors in the stylus locate mode and the stylus
tracking mode. In the locate mode, the distance between any three
adjacent vertical array conductors and the next occurrence of any
of those conductors that is attached to the same bus wire, must be
greater than the maximum height 62 at which a locate operation can
begin, as is shown in FIG. 3. For the tracking mode, the distance
between any group of adjacent wires that are driven simultaneously
during the tracking operation, as shown in FIGS. 4-7, with respect
to the next occurrence of another conductor connected to the same
bus wire, must be greater than the expected displacement of the
stylus which may occur during one complete tracking position
determination cycle. This is typically approximately 0.75 inches.
Added to this is the constraint necessary to accomplish capacitance
finger touch sensing. Fingers are sensed by the change in
capacitance when the fingers cover the transparent array
conductors. Low force touches only change the capacitance of two
adjacent conductors. The bus wire attachment sequence must be
patterned so that the finger sensing portion of the system can
identify capacitance changes in two adjacent conductors as a touch,
which is unique and will not occur for any other combination of
adjacent conductor pairs in the array. The essential finger sensing
constraint is that only one pair of adjacent conductors in the
array should be connected to the same pair of bus wires. In a 16
wire bus such as the X bus 80, there are 120 unique combinations of
adjacent pairs of wires which will satisfy this condition. If there
were a quantity of N bus wires in the bus, then there would be
N(N-1) divided by 2 unique combinations of adjacent pairs of
conductors which will satisfy this condition. The bus wire
attachment pattern requirement is to select a sequence that meets
these adjacent conductor constraints and which maintains an
adequate grid distance between groups of wires which are attached
to the same bus wire. The allowable bus wire attachment sequences
will differ for different numbers of bus wire elements N and for
different numbers of array conductors X for vertical conductors.
The greater the number of bus wires, the easier it is to meet the
physical constraints on tracking speed and the threshold distance
for stylus detection, for a given size overlay. All of the above
considerations apply equally to the horizontal Y array conductors
as they do for the vertical X array conductors.
Table I and FIG. 15 represent an optimum bus connection sequence
for the condition that the bus contains 16 bus wires which are
connected to 112 transparent array conductors. The pattern was
created by interleaving ascending and descending sequences of bus
wires for most of the array conductors and then making special
adjustments at the end to fill out the set of 112 array conductors
in either the horizontal or the vertical direction.
FIG. 11 shows the general layout of the overlay 20 and shows the
relative position of the four bolt holes 186 through which the
bolts 36 of FIG. 2 pass, enabling the mounting of the overlay 20
onto the face of the CRT 24. The display input area 188 is shown in
cross-sectional view in FIG. 12. The overlay is comprised of two
major portions, the inner laminate 56 and the outer laminate 58
which are attached as shown in FIG. 12 by the adhesive layer 52'.
The inner laminate 56 is stretched upon the outer surface of the
glass face 32 of the CRT 24. The inner laminate 56 has an
anti-newton ring coating 53 which is applied to the display side of
the overlay to eliminate newton rings when the inner laminate comes
into contact with the glass face 32. An electrostatic shield layer
51 consists of a full panel coating of indium tin oxide which is
grounded. This coating shields the vertical X conductors and
horizontal Y conductors from electrostatic noise generated by the
cathode ray tube 24. The electrostatic shield layer 51 must be less
than 100 ohms per square and must exceed an optical transmissivity
of 80 percent. The inner substrate layer 50 is an optically clear
layer of polyethylene terephthalate onto which is magnetron
sputtered the transparent wire coating of indium tin oxide which
will result in the vertical transparent conductors X1, X2, etc. The
indium tin oxide coating is etched to provide 0.025 inch wide lines
on 0.125 inch center line spacing. The resistance of the indium tin
oxide layer must not exceed 80 ohms per square. There are 112
transparent, vertical conductors X1, X2, . . . X112. The outer
substrate layer 54 of the outer laminate 58 is substantially the
same as the inner substrate 50 and the indium tin oxide transparent
conductor layer deposited on the outer substrate 54 has the same
properties as the indium tin oxide transparent wire layer deposited
on the inner substrate 50. The horizontal Y conductors Y1, Y2, . .
. Y112 on the outer substrate 54 are oriented at right angles with
respect to the vertical X conductors deposited on the inner
substrate 50. During manufacture, the inner laminate 56 is built up
as a composite and is coated with the insulation layer 52 which is
a thin layer of ultraviolet initiated vinyl acrylic polymer.
Similarly, during manufacture, the outer laminate 58 is coated with
the insulation layer 52" which is identical in composition with the
insulation layer 52. After the inner laminate 56 and the outer
laminate 58 have been respectively constructed as separate
composites, they are joined with the adhesive layer 52' which has
the same composition as the insulation layer 52. The resulting
overlay composite 20 has an overall thickness in the display input
area 188 of approximately 0.005 inches, has a high optical
transparency, and has a durable mechanical quality. The overlay 20
can be stretched and bent within limits to conform to the curvature
of the cathode ray tube display surface, without rupturing the
electrical continuity of the transparent conductors in the array.
In an alternate embodiment, the X and Y array conductors could be
deposited on the outer laminate 54 and the inner laminate 56,
respectively.
FIG. 13 shows a front view of the X bus 80 for the overlay 20 and
FIG. 14 shows a side cross-sectional view, illustrating how the bus
wire 3 is electrically connected to the transparent array conductor
X2. When the insulation layer 52 is applied to the surface of the
inner laminate 56, it is deposited in a printing operation such as
silk screening so that the array of apertures 180 and 180' as shown
in FIGS. 13 and 15 are left open exposing selected transparent
conductors. Thereafter, silver ink bus wires 1-16 are deposited on
the outer surface of the insulation layer 52 so that they pass over
selected ones of the apertures 180 and 180', thereby making
electrical contact with the selected, exposed array conductors. For
example, as is shown in FIG. 13 and FIG. 14, the bus wire 3 passes
through the aperture 180 in the insulation layer 52 and makes
electrical contact with the vertical transparent conductor X2. The
resistance of the silver ink bus wires 1-16 does not exceed 20 ohms
per inch for a 0.015 width line. The thickness of the bus wires
does not exceed 0.001 inches.
FIG. 9 shows an architectural diagram of the detection system. The
vertical conductors X1-X112 are connected through the X bus 80 to
the wire select multiplexer 112 and the horizontal Y conductors
Y1-Y112 are connected through the Y bus 90 to the wire selection
multiplexer 112. The radiative pickup stylus 60 is connected
through the gate 120 to the radiative pickup measurement device
122. The wire selection multiplexer 112 is connected through the
mode multiplexer 116 to the capacitance measurement device 128
which is used for capacitance finger touch detection. The wire
selection multiplexer 112 is also connected through the mode
multiplexer 116 to the 40 kilohertz oscillator driver 126 which is
used to drive the X bus 80 and the Y bus 90 for the stylus
detection operation. The mode multiplexer 116 also has an enabling
output to the gate 120 to selectively connect the output of the
stylus 60 to the radiative pickup measurement device 122, for
stylus detection operations. The output of the capacitance
measurement device is connected through the analog-to-digital
converter 130 to the processor address/data bus 110. The output of
the radiative pickup measurement device 122 is connected through
the analog-to-digital converter 124 to the bus 110. A control input
114 to the wire selection multiplexer 112 is connected to the bus
110 and the control input 118 to the mode multiplexer 116 is
connected to the bus 110. The processor address/data bus 110
interconnects the control processor 100 with the read only memory
(ROM) 104, the random access memory (RAM) 102, and the I/O
controller 106. The I/O controller 106 has an I/O bus 108 which
connects to a host processing system such as the I/O bus of an IBM
Personal Computer.
The wire selection multiplexer 112 and the mode multiplexer 116
connects selected patterns of a plurality of the horizontal and
vertical conductors in the overlay 20 to either the capacitance
measurement device 128 or the 40 kilohertz oscillator driver 126,
in response to control signals applied over the control inputs 114
and 118 from the bus 110 by the control processor 100. During
finger touch operations, the capacitance measuring device 128 has
its input coupled through the mode multiplexer 116 and the wire
selection multiplexer 112 to selected ones of the horizontal and
vertical conductors in the overlay 20 in response to control
signals from the control processor 100. The output of the
capacitance measurement device 128 is converted to digital values
by the converter 130 and is applied over the bus 110 to the control
processor 100, which executes a sequence of stored program
instructions to detect the horizontal array conductor pair and the
vertical array conductor pair in the overlay 20 which are being
touched by the operator's finger. In the stylus detection mode, the
40 kilohertz output of the oscillator driver 126 is connected
through the mode multiplexer 116 and the wire selection multiplexer
112 to selected ones of the conductors in the overlay 20, in
response to control signals applied over the control inputs 114 and
118 from the control processor 100. The electromagnetic signals
received from the overlay 20 by the stylus 60 are passed through
the gate 120 to the radiative pickup measurement device 122, which
measures those signals and provides an output which is digitized by
the converter 124 and output to the control processor 100. The
control processor 100 executes a sequence of stored program
instructions to detect the proximity of the stylus to the overlay
20 in the proximity detection mode and then to locate and track the
horizontal and vertical position of the stylus with respect to the
overlay 20 in the location and tracking mode. The stored program
instructions for carrying out these operations can be stored in the
read only memory 104 and/or the RAM 102, for execution by the
control processor 100. Positional values and other result
information can be output through the I/O controller 106 on the I/O
bus 108 to the host processor for further analysis and use in
applications software.
FIG. 10 is a flow diagram of a first embodiment of the invention
where either finger touch operations or alternately stylus
detection operations can be carried out, one to the exclusion of
the other during a particular sensing interval. During the
proximity search mode, the capacitance finger touch operations are
interleaved with the radiative stylus pickup operations to
determine whether either a finger touch has been initiated or a
stylus has been brought into threshold proximity to the overlay 20.
When either of these conditions are found, the stored program
instructions represented by the flow diagram of FIG. 10, will lock
out the opposite search sequence and will proceed to the locate
sequence for the finger touch or for the stylus detection,
whichever has been sensed.
This alternate scanning for either the initiation of a finger touch
or the beginning of stylus detection is carried out by steps
140-148 and 154-160 of the flow diagram of FIG. 10. In step 140,
the X-drive sequence is updated followed by step 142 where the
touch sensing function of the capacitance measurement device 128 is
turned on by appropriate control signals to the mode multiplexer
116 and the wire selection multiplexer 112. Then in step 144 the X
axis conductors in the overlay 20 are sensed by the capacitance
measurement device 128. In step 146 the signal strength for
capacitive coupling by a finger touch is determined by the control
processor 100. Control processor 100 then determines whether the
touch threshold has been crossed in step 148. If the touch
threshold has been crossed, the program transfers to step 150 to
the touch locate mode. If the touch threshold has not been crossed,
the program transfers to step 154 to determine whether the stylus
has come into close proximity to the overlay 20. In step 154, the
mode multiplexer 116 disconnects the capacitance measurement device
128 and connects the 40 kilohertz oscillator driver 126 to the
overlay 20 through the wire selection multiplexer 112. The mode
multiplexer 116 also enables the gate 120 so that the received
signals by the stylus 60 can be passed to the radiative pickup
measurement device 122. In step 156, proximity sensing operations
are carried out by the oscillator driver 126 driving a plurality of
either the X conductors or the Y conductors or both X and Y
conductors in the overlay 20 and by the radiative pickup
measurement device 122 determining whether the stylus 60 has
received a sufficiently large magnitude signal to indicate close
proximity of the stylus to the overlay. In step 158, the signal
strength measured by the radiative pickup measurement device 122 is
analyzed by the control processor 100 and in step 160 the control
processor 100 determines whether the stylus threshold has been
crossed. If the stylus threshold has not been crossed, then the
program returns to step 140 to check again as to whether a finger
touch has been initiated. If the stylus threshold has been crossed
in step 160, then the program passes to step 162 for the stylus
locate and tracking mode to begin.
When the touch threshold has been crossed, as determined by step
148, the program passes to step 150 where the touch locate mode
begins. The capacitance measurement device 128 is connected through
the mode multiplexer 116 and the wire select multiplexer 112 and
the capacitance of each respective vertical bus wire 1-16 in Y-bus
90 and each respective horizontal bus wire 1-16 in X-bus 80 is
measured and their values digitized by the converter 130 and output
over the bus 110 to the control processor 100. The control
processor 100 identifies the unique pair of the 112 vertical X
conductors XI and XI+1 having the highest capacitance and that is
attributed as the horizontal position of the finger touch.
Correspondingly, the unique pair of the 112 horizontal Y conductors
YJ and YJ+1 having the highest capacitance values are identified
and those are attributed as the vertical location for the finger
touch. This information is output by the control processor 100
through the I/O controller 106 to the I/O bus 108.
If the stylus detection threshold is crossed in step 160, then the
stylus locate and tracking mode in step 162 commences. The vertical
X conductors X1-X112 are energized in groups of at least six
conductors in a manner previously described for FIGS. 4-7, and the
magnitude of the electromagnetic signals radiated therefrom are
picked up by the stylus 60, measured by the radiative pickup
measurement device 122 and the digital values output from the
converter 124 are passed to the control processor 100. A similar
operation takes place for the horizontal Y conductors Y1-Y112 in
the overlay 20. The control processor 100 then processes these
signals to locate the horizontal and vertical position of the
stylus with respect to the overlay 20 and this resultant
information is output through the I/O controller 106 to the I/O bus
108. The operation of tracking the consecutive positions of the
stylus 60 with respect to the overlay 20 then takes place by
sequentially updating the position of the stylus 60. If the
magnitude of the signals received by the stylus 60 diminishes as
determined in step 166, the program then passes back to step 140
where the finger touch initiation and stylus proximity detection
operations are alternately carried out.
A second embodiment of the invention is shown in FIGS. 16-19 where,
instead of locking out either the finger touch operation or the
stylus detection operation when the other is being conducted, in
the second embodiment both finger touch and stylus detection
operations can be carried out simultaneously. This is achieved by
multiplexing stylus detection and finger touch sensing in the
proximity loop 200, multiplexing stylus location and finger touch
sensing in the locate cycle 220, and multiplexing track stylus
location detection and finger touch sensing in the tracking loop
240, as shown in the flow diagram of FIG. 16.
FIG. 16 shows the proximity loop 200 including steps 202-210 and
FIG. 17 shows the timing diagram which includes the stylus
proximity loop 200. As was previously mentioned, stylus proximity
is determined by radiating a uniform 40 kilohertz signal from the
overlay 20 and determining whether the stylus 60 is picking up a
sufficiently large amplitude representation of that signal to pass
a threshold value. This is represented by step 202 of the proximity
loop 200. In step 204, the control processor 100 determines if the
threshold has been passed and if so, the control processor 100 sets
a flag S1. Whether the stylus proximity threshold has been exceeded
or not, the program then passes to step 206 where the finger touch
sensing operation takes place, during which the capacitance
measurement device 128 is sequentially connected to each of the 16
bus wires in the X bus 80 and each of the 16 bus wires in the Y bus
90. The control processor 100 determines in step 208 whether the
capacitance for any of the vertical array conductors X1-X112 or any
of the horizontal Y conductors Y1-Y112 is greater than a threshold
value and if it is, then the adjacent pair of vertical array
conductors and the adjacent pair of horizontal array conductors
which have the highest measured capacitance, are identified by the
control processor 100 and attributed as the location of a finger
touch which is output by the I/O controller 106, as previously
described. The program then passes to step 210 to test whether the
flag S1 is on or off indicating whether the proximity threshold for
stylus detection was passed in step 202. If S1 is still off, then
the program returns to step 202 to once again test for the
proximity of the stylus. This operation for the stylus proximity
loop 200 is shown in the timing diagram of FIG. 17. The control
processor 100 can access a table stored in the RAM 102 and perform
a table lookup to determine the correlation between the 16 bus
wires in the X bus 80 and the corresponding vertical conductor
adjacent pairs and also the 16 bus wires in the Y bus 90 and the
corresponding horizontal adjacent conductor pairs, thereby speeding
up the operation of finger touch location.
If step 202 detected that the stylus had come within the threshold
proximity distance to the overlay 20, then the flag S1 would have
been turned on and step 210 would have passed program control to
the locate cycle 220. This would involve the passage of the program
to step 222 where the stylus location procedure, as described
above, would be carried out for the vertical array conductors
X1-X112 and then the program would pass to step 224 to perform a
similar stylus location operation for the horizontal array
conductors Y1-Y112. Here again, tables can be stored in the RAM 102
which correlate detected amplitude maximum by the stylus 60 with
the position attributable to the stylus in the horizontal and
vertical directions. In step 222, the control processor 100 will
output the X location attributed to the stylus 60 and in step 224
the control processor 100 will output the Y location attributed to
the stylus 60, in the same manner as was described above. The
locate cycle 220 then passes control to step 226 where, once again,
the finger touch sensing operation takes place in a manner similar
to that described for step 206. If an increased capacitance for the
array conductors is detected in step 226, then the control
processor 100 in step 228, will output the coordinates for the
finger touch through the I/O controller 106 to the I/O bus 108, as
previously described for step 208. Note that both the stylus
location and the finger touch location can be separately and
substantially simultaneously output by the control processor 100
over the I/O bus 108 during the locate cycle 220. This can be seen
for the representation of the stylus locate cycle 220 in FIG.
17.
The program then passes to the tracking loop 240 as shown in FIG.
16 and for which a timing diagram is shown in FIG. 17. Step 242
tracks the stylus X location, computing the offset distance in the
X direction, followed by step 244 which tracks the stylus in a
similar manner for the Y direction. In steps 242 and 244, the
control processor 100 outputs over the I/O bus 108, the
periodically updated horizontal and vertical position attributed to
the stylus 60 with respect to the overlay 20. The program passes to
step 246 which conducts another finger touch sensing operation in a
manner similar to that described for step 206. In step 246, if a
finger touch is sensed, step 248 has the control processor 100
outputting the coordinates of the finger touch on the I/O bus 108,
in a manner similar to that described for step 208. Note that
during each cycle of the tracking loop 240, horizontal and vertical
coordinates representing the position attributed to the stylus 60
and horizontal and vertical coordinates attributed to the position
of the finger touch can both be output, substantially
simultaneously, by the control processor 100 to the I/O bus 108. In
step 250, the control processor 100 determines whether the
amplitude of the signal received by the stylus 60 is less than the
threshold value for proximity detection. If the magnitude is
greater than the threshold value, then the program passes to step
242, continuing the tracking loop cycle. If the magnitude of the
signal detected by the stylus 60 is less than the threshold value,
then the program passes back to the proximity loop 200 and restarts
step 202 for the remote proximity stylus sensing operation. This is
shown for the stylus tracking loop 240 as depicted in the timing
diagram of FIG. 17.
Thus it is seen that in the second embodiment of the invention, the
system can be operated so as to provide the simultaneous detection
of both the pickup stylus 60 and a finger touch. This is depicted
in FIG. 19, which is a view of the display as seen through the
overlay 20, showing the simultaneous display of the touch cursor
270 whose location is produced by the host computer based upon the
coordinates for the finger touch output over the I/O bus 108 by the
control processor 100. Also depicted in FIG. 19 is the display of
the stylus cursor 260, whose image is produced by the host
processor, based upon coordinates for the stylus which are output
over the I/O bus 108 by the control processor 100.
FIG. 18 depicts an example memory organization for the RAM 102 in
the second embodiment of the invention, where the RAM 102 is
connected by the processor bus 110 to the control processor 100, as
is seen in FIG. 9. The RAM 102 can be partitioned into a sequence
control routine which is a sequence of stored program instructions
which carries out the operation depicted in the flow diagram of
FIG. 16. The stylus proximity routine, the stylus locate routine
and the stylus tracking routine are each a sequence of stored
program instructions for carrying out the respective operations of
proximity detection, location and tracking of the stylus, as
previously described. A finger locate routine is a sequence of
stored program instructions to carry out the operation of locating
the coordinates of a finger touch, as previously described.
Multiplex control registers and measurement control registers can
be provided in the RAM 102. Optionally, a cursor shape table can be
included in the RAM 102 to define the shape of the touch cursor 270
and the stylus cursor 260, or alternately the function of the
cursor shape table can be carried out in the host processor. The X
bus wire capacitance value file and the Y bus wire capacitance
value file will provide temporary storage for the measured values
of each of the respective 16 bus wires in the X bus 80 and the Y
bus 90 during the finger touch sensing operations of steps 206, 226
and/or 246 of FIG. 16. After those stored capacitance values are
processed by the control processor 100, the identity of the two bus
wires in the X bus 80 and the two bus wires in the Y bus 90
corresponding to the maximum measured capacitance can be stored in
the bus files partitioned in RAM 102 of FIG. 18. The finger X
location table and the finger Y location table are also shown
partitioned in the RAM 102. After the operation of the control
processor 100 in conducting the table lookup for the X location and
the Y location of the finger touch, the X and Y coordinates for the
finger touch can be temporarily stored in the RAM 102 before being
output over the I/O bus 108. Similarly, an X bus wire radiation
value file and a Y bus wire radiation value file is provided for
the temporary storage of measured values of radiation received by
the stylus 60 corresponding to three bus wire pairs, as previously
described. Bus file partitions, stylus X location and stylus Y
location lookup tables, and array files are provided in the RAM 102
to facilitate the control processor 100 carrying out the stylus
location and tracking operations. The final computed value for the
X and Y coordinates of the stylus can then be temporarily stored in
the RAM 102 before being output over the I/O bus 108, as previously
described.
A utilization routine can also be included in a partition in the
RAM 102, which consists of a sequence of stored program
instructions for carrying out cooperative operations between the
finger touch detection and stylus detection operations described
above. For example, a utilization routine can be provided to
identify when finger touches occur in a region vertically below the
coordinates for stylus detection, with the finger touch being in an
otherwise prohibited area. This may indicate that the user has
rested the palm of his hand on the surface of the overlay 20 while
positioning the stylus 60 at the desired point. The utilization
routine can be selectively controlled to mask outputting the finger
touch coordinates in such a situation, if desired by the
operator.
The resulting combined finger touch and stylus detection system
provides an enhanced man-machine interface, enabling either the
sequential or simultaneous detection of both stylus position and
finger touch, thereby increasing the range of applications for
interactive input devices. The resulting invention has a reduced
bus size and is adaptable for use with a variety of display types
having both flat and convex display surfaces. The structure of the
overlay permits low cost manufacture and long-term reliability.
Although specific embodiments of the invention have been disclosed,
it will be understood by those having skill in the art that minor
changes can be made to the form and details of the specific
embodiments disclosed herein, without departing from the spirit and
the scope of the invention.
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